1. Field of the Invention:
This invention relates to the collection of solar energy, and, more particularly, to the collection of solar energy by focusing the solar energy from a parabolic mirror into a conduit or pipe which is in physical contact with the parabolic mirror.
2. Description of the Prior Art:
A typical design of solar collector apparatus comprises a grid of pipes, either metal or plastic, usually painted black so as to absorb a maximum amount of radiant energy, connected in parallel with headers or manifolds at both ends of the pipe grid. The pipe grid, with headers, is generally disposed also on a black surface for again trapping a maximum amount of radiant energy. The diameter or size of each individual pipe is generally rather small. A fluid, typically water, flows through the apparatus and absorbs heat as it flows through the pipes. With a small volume of water moving in the pipes, maximum heat transfer is accomplished between the pipe and the water. A large volume of water is heated due to the size of the grid array.
The collector described in the preceding paragraph has numerous variations, primarily in the design of the headers and tube grids used. To increase the efficiency of such heater apparatus, the collectors may be installed at an angle with respect to the earth so as to optimize the angle of the radiation from the sun to the collector. For more sophisticated, but more expensive, arrays, the collector apparatus may even rotate from east to west to maintain as normal an inclination as possible with respect to the sun.
An alternate system to the array of pipes and headers is a spiral grid in which a conduit or pipe is arrayed in a spiral configuration with the coils of the spiral adjacent and touching each other. Again, the concept is to obtain a maximum efficiency in the collection of solar radiation, and such is accomplished by having the coils disposed adjacent each other. Fluid flowing through the coils is heated and may be transferred from a single coil to either a reservoir or to an adjacent coil where the temperature of the circulating fluid can be raised before being ultimately transferred to a reservoir.
Another type solar collector comprises a series of parallel parabolic channels with a pipe or tube disposed along the channel at the focal point of rays impinging on the parabolic reflector. A pipe or tube is disposed parallel to the channel at the focus of the parabolic curve to absorb the radiant heat impinging upon the reflective surface of the parabola and focused at the pipe or conduit. The radiant heat energy is thus concentrated along the pipe and transmitted to fluid flowing within the pipe.
Still another prior art apparatus comprises a series of convolutions or corrugations which are used as channels for a fluid to flow directly over them. That is, a fluid, such as water, flows by gravity within the corrugations or channels and absorbs heat energy from the corrugated sheet. This type of collector includes a transparent sheet, such as plastic, over the top of the apparatus to minimize evaporation of the fluid during the heat absorption of the fluid.
Obviously, all of the various types of solar collectors may be disposed at an angle to the earth for maximum radiation reception, and, if desired, may also pivot from east to west to maintain the desired normal orientation with the sun. If a solar collector is maintained in an orientation normal (perpendicular) to the sun, obviously maximum efficiency will be obtained with respect to the collection of solar energy.